Water feeding method for offset printing

ABSTRACT

A water feeding method for offset printing is provided using an ink consisting of a conventional offset printing ink and microcapsules containing a wetting or damping liquid. The microcapsules are decapsulated crushed on the ink distributing roller or vibrating roller of an offset press to be dispersed into the printing ink so that the dispersed printing ink may be applied to a plate clamped around the plate cylinder of the offset press.

United States Patent Kimura 154] WATER FEEDING METHOD FOR OFFSET PRINTING [721 Inventor: Taro Kimura, Tokyo, Japan [73] Assignee: Kabushiki Kaisha Ricoh, Tokyo,

Japan 22 Filed: March 16, 1971 211 App1,No.: 124,824

[30] Foreign Application Priority Data March 20, 1970 1 Japan ..45/24305 [52] US. Cl ..10l/45l, 101/148 [51] Int. Cl ..B4ll 25/14, B4lf 7/24 [58] Field of Search ..10l/450, 451, 452, 147, 148; 106/2, 14.5

[56] References Cited UNITED STATES PATENTS 2,090,704 8/1937 Rowell 101/450 Aug. 15,1972

3,608,483- 9/1971 Kaminstein ..101/452 FOREIGN PATENTS OR APPLICATIONS 903,724 8/ 1962 Great Britain ..101/450 Primary Examiner-J. Reed Fisher 7 Artorney-Burgess, Ryan and Wayne [57] ABSTRACT 1 Claim, 2 Drawing I BACKGROUND OF THE INVENTION The present invention relates to a water feeding method for offset printing and more particularly, to a water feeding method for offset printing using a novel offset printing ink into which is previously dispersed a microcapsulated wetting or damping liquid.

In the conventional offset press, a plate cylinder, a blanket cylinder and an impression cylinder are rotated between the side walls of the offset press. The plate clamped around the plate cylinder prints the inked image on the surface of the blanket cylinder and the printed image is then offset or transferred to the sheet as it presses through the press by pressure applied by the impression cylinder.

The inking mechanism, in general, comprises a form roller, a vibrating roller, an ink distributing roller, a duct roller, an ink fountain roller and an inking knife upon which is placed the printing ink. In addition to the inking mechanism, there is provided a water or wetting mechanism comprising a wetting liquid fountain containing the wetting liquid, a water fountain roller and a water vibrating roller which vibrates between the fountain roller and the vibrating roller so as to supply the wetting liquid to the vibrating roller to be mixed with the printing ink upon its surface.

The wetting liquid generally consists of water with or without suitable additive agents and serves to maintain the nonprinting areas of the plate repellent to greasy ink. This process is essential for reproduction of better quality prints.

In the conventional offset press of the type.

described, the wetting of the plate clamped around the platecylinder is effected by mechanical means. In addition, the quantity of wetting liquid to be applied must be precisely controlled. Consequently, the wetting or water mechanism and especially the mechanism driving the water roller is complicated in construction, which in turn results in the offset press being large insize and complex in construction and operation.

In the offset press of the type described, the wetting liquid is transferred from the wetting mechanism to the vibrating roller where the wetting liquid and ink form a water-in-oil emulsion. When this emulsion is fed to the printing plate, ink is selectively applied onto the printing areas while the wetting liquid is applied onto the non-printing areas. It is desirable that the water-in-oil emulsion contains water in the order of 50 percent by weight relative to the whole weight of the emulsion so that the wetting liquid and ink may be smoothly applied to the non-printing and printing areas, respectively. Therefore, if such an emulsion is previously prepared, it may be supplied to an offset press which is not provided with a wetting mechanism. However, in the water-imoil emulsions in which the wetting liquids are in excess of 30 percent by weight, it is quite unstable because the wetting liquids and inks tend to separate from each other as time elapses. Consequently, it is extremely difficult to store such emulsions in the emulsified state for a long time. In addition, when water is dispersed in the printing ink in the order of 50 70 percent by weight, it is impossible to prepare a water-in-oil' type emulsion.

SUMMARY OF THE INVENTION An object of the present invention is to avoid the disadvantages described above characterizing the conventional offset printing.

Another object of the present invention is to simplify the construction of the mechanisms of the offset press.

Yet another object of the present invention is to providea process for the simultaneous application of both a wetting liquid and a printing ink to a printing plate of an offset press by use of a novel offset printing ink.

A further object of the present invention is to provide an offset press which does not require a separate wetting mechanism for printing. The novel ofiset printing ink consists of a conventional offset printing ink and microcapsules containing a wetting or damping liquid. When the printing ink is applied to the offset press, the microcapsules mixed with the greasy ink are destroyed or crushed on an ink distributing roller or vibrating roller of the offset press and the wetting liquid is dispersed in the greasy ink. The dispersed printing ink is applied to a plate clamped around the plate cylinder of the offset press and the liquid serves to maintain the nonprinting areas of the plate repellent to the greasy ink as same as liquid supplied by the conventional method.

In the present novel printing ink, the wetting liquid and ink will not separate from each other after they are mixed even after prolonged storage. In addition, the novel printing ink'is a water-in'oil emulsion which is best suited for application from a vibrating roller wetting liquid and ink on to a printing plate.

The present invention will become more apparent from the description of the embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram of aconventional offset press illustrating the simultaneous application of wetting liquid and printing ink of the present invention;

solution microcapsulated in accordance with the present invention.

PREFERRED EMBODIMENT OF THE INVENTION Briefly, in accordance with the present invention, microcapsules containing wetting liquid are mixed with a conventional greasy offset printing ink.

Referring now to FIG. 1, the conventional offset press will be described briefly. A plate cylinder 2, a blanket cylinder 3 and an impression cylinder 4, etc. rotate between the side walls 1 of the offset press. The plate clamped around the place cylinder 2 prints the inked image on the surface of the blanket cylinder and the printed image is then offset or transferred to the sheet (not shown) as it passes through the press by pressure applied by the impression cylinder 4.

The inking mechanism comprises a pair of form rollers 5 and 6, a vibrating roller 7, a duct roller 8, an ink fountain roller 9, and an inking knife 10 upon which is placed printing ink 11. In addition to the inking mechanism, there is provided a watering or damping mechanism comprising a damping liquid fountain 12 containing wetting liquid W, a fountain roller 13 and a water roller 14 which vibrates between the fountain roller 13 and the distribution cylinder 7 so as to supply' the wetting liquid W to the distribution cylinder 7 to be mixed with the printing ink upon its surface.

The wetting liquid W generally consists of water with or without suitable additive agents and serves to maintain the nonprinting areas of the plate repellent to greasy ink. This process is essential for the reproduction of better quality prints.

In the conventional ofiset press of the type described, the damping of the plate clamped around the plate cylinder 2 is accomplished by mechanical means. In addition, the quantity of wetting liquid W to be applied must be precisely controlled. In order to accomplish this effect, the damping or watering mechanism and especially the mechanism driving the water roller 14 is a complicated structure. Because of this structure, the offset press is not only large in size but also complex in construction and in its operation.

It is desirable that the inking and watering or damping mechanisms which are used to prepare the waterin-oil type emulsion contain about 50 percent water, by weight, so that the nonprinting areas of the plate may be suitably moistened or damped while the printing areas are suitably applied with the printing ink. For this purpose, there has been proposed a method for directlysupplying onto the offset press with a previously prepared water-in-oil emulsion containing about 50 percent water and about 50 percent printing ink. However, it is impossible to prepare a stable emulsion where there is more than 30 percent water. In addition, when water dispersed in the printing ink is 50 to 70 percent by weight, it is impossible to prepare the water-in-oil type emulsion suitable for printing.

According to the present invention, the wetting liquid W is capsulated within a capsule 21 as shown in FIG. 2 by a chemical process. The microcapsules are dispersed in the printing ink at a predetermined ratio prior to their being supplied to the inking mechanism of the offset press. The microcapsules 21 are decapsulated by the distributing cylinder or the vibrating cylinder and the liquid is dispersed in the greasy ink to provide a most suitable water-in-oil type emulsion.

In the present invention there are used the wetting liquid W which is water or an aqueous solution including suitable additive agents. They are for example:

1. The wetting liquid for electrofax offset printing consisting of ferrocyanides such as potassium ferrocyanide and sodium ferrocyanide a phosphates such as sodium phosphate tribasic, ammonium phosphate monobasic, ammonium phosphate dibasic, sodium pyrophosphate, sodium triphosphate and sodium ammonium hydrogen phosphate as a principal component a organic acids such as oxalic acid, citric acid and ammonium citrate dibasic and glycols such as ethyleneglycol and in the order of l to 100 microns'by the following methods: I. Microcapsulation by Under-liquid Spray-drying:

A water-in-oil (W/O) type emulsion was prepared by emulsifying 30 cc of the above-mentioned wetting liquid into 150 cc of a 10 percent solution of polystyrene in benzene. To this was added under vigorous agitation 1 liter of 2 percent aqueous solution of gelatin as a minute jet stream. Thus, a complex emulsion of water-in-oil in water (W/O)/W type was obtained. Then, the temperature of the system was raised to 40 C under agitation. By keeping the agitation at this temperature for about 2 hours, polystyrene capsules having a diameter of about 100 p. and containing the wetting liquid therein were obtained.

11. Microcapsulation by lnterfacial Polymerization:

50 cc of the above-mentioned wetting liquid were added to a solution of 0.4 mol of 1,6-hexamethylenediamine and 0.45 mol of sodium carbonate in 100 cc of water. This mixture was emulsified into a mixed solvent of chloroform and cyclohexane in the ratio of 1:3 (volume). To the emulsion thus obtained was added'slowly a solution of 0.6 g of phthaloyl dichloride in cc of the same solvent as the abovementioned mixed solvent. By keeping the temperature of the system at 0 C to 4 C, microcapsules having a diameter of 10 p. to 50 p. and containing the wetting liquid were obtained. These microcapsules were separated by centrifugal separator.

III. Microcapsulation by Coacervation:

cc of the above-mentioned wetting liquid were added to 400 cc of a mixture of xylene and carbon tetrachloride in the ratio of 1:1, said mixture containing 5 percent of ethyl cellulose, to prepare an emulsion. After the emulsion was diluted by adding 400 cc of carbon tetrachloride to it, petroleum ether was added slowly to the diluted emulsion, while the temperature of the system was kept at 10 to 12 C and the agitation was continued. When 800 cc of petroleum ether had been added, a thick solution of ethyl cellulose came out around the wetting liquid and surrounded it. Microcapsules containing the wetting liquid thus obtained were separated by decantation.

The microcapsules containing the wetting liquid were dispersed into printing ink or emulsified printing ink. Examples of the present'invention will be shown below:

Example 1 The following constituents were uniformly mixed and dispersed:

conventional offset printing ink 50 parts aqueous solution of ammonium hydrogen phosphate 25 parts surface active agent 0.4 parts Thereafter, to the emulsion of the above constituents were added and uniformly dispersed 40 parts of the microcapsules containing the wetting liquid which were prepared by the aforesaid coacervation procedure and the wall membrane of which was made of ethyl cellulose.

Thus, the prepared printing ink was applied to the plate through the vibrating roller and prints with a better image quality and high reproducibility were obtained. Better results were obtained for both of the master paper plate prepared by Electrofax system and the conventional P.S.plate (pre-sensitizing plate).

Example 2 First the emulsion of the following constituents was prepared:

conventional offset printing ink I 50 parts ammonium hydrogen phosphate 25 parts surface active agent 0.4 parts To this emulsion were added and uniformly dispersed 40 parts of the microcapsules containing the wetting liquid which were prepared by the aforesaid interfacial polymerization and the wall membrane of which was made of polyamide.

The printing ink was applied to the plate through the vibrating roller and superior results were attained as in the case of Example 1.

The microcapsules of the present invention are decapsulated upon the vibrating roller and remain upon it and the plate clamped around the plate cylinder, but their diameters or particle sizes are very fine so that their presence will not impair the printing at all.

According to the present invention, the wetting solution may be supplied in the form of the microcapsulated wetting solution of the previously suitably prepared composition with respect to the printing ink to be used, so that the water mechanism in the conventional offset press may be advantageously eliminated.

Furthermore, the properties of printing ink into which b. crushing said microcapsules on said roller resulting in the dispersing of said wetting liquid into said ink, and t c. applying said ink, into which wetting liquid has been dispersed, to a plate clamped around the plate cylinder of said offset press. 

1. A water feeding method for offset printing comprising the steps of a. applying an offset printing ink having dispersed therein microcapsules each of which consists of a wall membrane and wetting liquid contained therein to one of the ink distributing rollers and the vibrating roller of an offset press, b. crushing said microcapsules on Said roller resulting in the dispersing of said wetting liquid into said ink, and c. applying said ink, into which wetting liquid has been dispersed, to a plate clamped around the plate cylinder of said offset press. 